ffmpeg7: fix compilation for OS X 10.7 through 10.12

Add typedef for AVMediaType when compiling against older SDK versions
that use NSString* directly.

Fixes: https://trac.macports.org/ticket/70519

multimedia/ffmpeg7/Portfile

@@ -106,6 +106,10 @@ patchfiles-append   patch-libavcodec-profvidworkflow.diff
 # TODO: Raise the issue to upstream
 patchfiles-append   patch-libavcodec-librsvgdec.diff
 
+# Typedef AVMediaType to NSString* on older systems
+# Patch submitted to upstream, remove once upstream has included it
+patchfiles-append   patch-libavdevice-avfoundation.diff
+
 # https://trac.macports.org/ticket/68720
 # Remove once upstream has included these in the next release
 # patchfiles-append   patch-issue-10695.diff

multimedia/ffmpeg7/files/patch-libavdevice-avfoundation.diff

@@ -0,0 +1,14 @@
+--- libavdevice/avfoundation.m
++++ libavdevice/avfoundation.m
+@@ -763,6 +763,11 @@ static int get_audio_config(AVFormatContext *s)
+     return 0;
+ }
+
++#if (defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE && __IPHONE_OS_VERSION_MAX_ALLOWED < 110000) || \
++    ((!defined(TARGET_OS_OSX) || TARGET_OS_OSX) && MAC_OS_X_VERSION_MAX_ALLOWED < 101300)
++typedef NSString* AVMediaType;
++#endif
++
+ static NSArray* getDevicesWithMediaType(AVMediaType mediaType) {
+ #if ((TARGET_OS_IPHONE && __IPHONE_OS_VERSION_MIN_REQUIRED >= 100000) || (TARGET_OS_OSX && __MAC_OS_X_VERSION_MIN_REQUIRED >= 101500))
+     NSMutableArray *deviceTypes = nil;